Hydraulic jack



J. LOEF HYDRAULIC JACK Jan. 6, 1953 wn/mp 1 JA/fa 0f/f Arr/3 PatentedJan. 6, 1953 UNI-TED STATES PATENT OFFICE 1949,' Serial No; 86,471October 1; 1948 'v claims. (c1. en -52.)

Applicatinn April 9, InGermany This yinvention relates .to hydraulicunits. for lifting tackles. such as lifting. jacks for, vehi-cles, lift.trucks and similar devices equipped with hydraulic units consisting of apump unit, a motor unit, a reservoir for the hydraulic fluid, andthecustomary accessory equipment.

Limiting the maximum travel of the motor unit'in hydraulic devices ofthis character is ordinarily accomplishedby the `useof mechanical stops.Since the forces involved are very large, these stops must be ofrelatively large dimensions. In spite of their large size, breakageofthe stops occurs relatively frequently.

This invention deals with the problem of providing means for limitingthe maxi-mum travel of the mot-or piston which is especially intendedfor utilization in apparatus in which the pump piston, p ump cylinder,motor piston, motor cylinder and storage reservoirare'arranged'cof'axi'ally The sole''gure shows an embodiment of my in`vention wherein the pump unit 4, Zis co-axially positioned withinthemot'orlp'iston II.` This 'arrangement ofthe pump unit inthe hollowmotor piston vII ofthe motor unit I, II permits limiting the stroke ofthe motor piston vI I, or ofthe motor cylinder I, without the'necessityYfor providing stops'or providing slits in the compression cylinder I. Inthisway difficulties in operation which might otherwise occur because ofthe presence of such 'stop members. are, to a very great extent,completely avoided.

Referring specifically to the drawing, the motor-'piston I I is hollow.Pump cylinder!! with its pump; piston .29 are positionedwithinitliemotor piston II.A A' cylindrical continuation 62 ofthe mot-or pistonA II isy also hollow, vand is in communication with the'pumping cavitywithin the motor piston. It is traversed by the pumppistcn 2D; which isVformed withthe eye 6 vat its end.' This eye, in the con-structionshown, is situated betweenthetwo cheeks 1, which are carried Vby thecontinuation 62, or by arotatable ring 13,'so that there can berelativeaxial movement between the cheeks 1 and the pump piston 20. Theinterior of 'extension'IZ vserves as a supply reservoir 33 -for thehydraulic liiuid.

The -wall- 62'of reservoir 33 is stiiened by a reinforcement' Yat-theend opposite to eye 6. At the outer periphery of` the reinforcement 80,

there'is a jacket 1 I, fastened thereto by screws or4 bolts 12'. Thisjacket .or shell surroundsvthe compression cylinder, formingtherebetween an intermediateI space or interstice 10. Jacket 1I isprovided near the end of .the motor pistoni I with flanges 31 on oneside, lout. `it iis. otherwisecpen on this side. Inthe intermediatespacelil there is av return compression spring 38, whichserves `forlowering or restoring the device to its initial condition when no loadis present. The abutments for compression spring 38 are formed by thebeads or flanges 31 on one end, and by closure member 52 of thecompression cylinder I at the opposite end.

The pump piston 20 is subjected to the action of .a return compressionspring 65, which spring, at one end, rests against ya recess'or shoulderin the pump piston 20 and, at the opposite end, rests against the righthand end of pump cylinderII. Along with lpump cylinder 4, there arepositioned in motor piston II an insert 1|4 for th-e suction valve 24,an insert 15 for motor check valve 21 and a brake valve 4 I, 42.

Theibrake valve for retarding the return stroke ofthe motor pistonconsists of a pin 4I which passes through the left end of motor pistonII and extends into the motor cylinder I. Com-l pression spring 28,acting on check valve ball 21, with its opposite end applies a load viaaplate or flange to the pin 4I, which is provided with a tapered keywayor fiuid passage 42.

intake valve support 45 is Ipositioned within the insert 114, the intakevalve support 445 containing intake check valve ball 24. Furthermore, apusher element 46 consisting of a pin ijs axially movable in support 45.Finally, insertion member 14 is further provided with a channel 41 andhollowedeout porti-on 48, which makes for the unimpaired ow of thepumping liquid to the motor piston check valve comprising -hall 21. PumppirstonZ has a conical recess 5l, the mouthedge 5t of which is intendedto enter into alternating action with inlet valve ball 2-4, while thebottom of the conical recess is intended to press against pin 46, theoppositerend of which acts on the outlet valve ball 21.

Displacement `of pump piston 2i) beyond its dead center or ordinarylimit of travel (to the left in the drawing), will cause piston 20 and aringlilre exten-sion thereof, 8i to lift the two check valve balls 24and 21 from their respective seats at the same time retaining .acircular configuration at the end of the piston 2li. The left end ofpiston 23 can therefore be turned at will without impairing the openingof the ball check valves.

Screwed into thei ront side of pump piston 20, there is va hollowthreaded plug 68, which `is intended to engage and displace pin 46 soas'to open 'the moto-r check valve 21. As the position of this threadedplug 68 is longitudinally adjustablewith respect to piston `2li.itsdistance awayl from :push

pin 46 can be varied, and it can thus lbe seen that substantiallysimultaneous opening of the two ball check valves 24 and 21 takes place.

In the present embodiment of my invention, a safety valve is disposedwithin the pump plunger 25. For vthis purpose, lanother hollow threadedplug 69 is screwed into plunger 20, behind threaded plug B8, its channelbeing closed by the springloaded safety valve ball I8. From safety valveball I8, an axial bore 22 in piston 20 leads, via a radial channel 1B,into an annular space 60 between pump cylinder 4 and compression pistonII.

An annular space S is provided between oompression piston II and thecompression cylinder I. Channel 49 of suction valve 24 leads into thisannular space and, furthermore, the wall of the compression cylinder I Iis provided with a channel 6I which connects the annular spaces 58 and60. Collar 59 of the motor piston closure member 52 is positioned toshut off the openings of channels 49 and 6i, said closure member closing01T the openings of pump intake channel 49 and the channel 6I leadingfrom the reservoir 33 into the annular space 58 upon completion of thefull stroke of motor cylinder I I.

The operation of my improved hydraulic unit will now be described.

The hydraulic liquid is drawn, upon the intake stroke of piston 2i] (tothe right), out of the reservoir 33, via the annular passage S9, theopening 6I the external annular passage 53 and the pump intake openingde, when the suction valve 24 is lifted. The power stroke of piston 2Qto the left forces the hydraulic recess 4B, the housing 42 of brakevalve 4I,

of spring 28 and the keyway into cylinder I. The return stroke of thepump piston 2d is eiected by the spring 65. In the course of the powerstroke compression cylinder I is moved to the left in the drawing. Inaccordance with the amount of pressure of the hydraulic uid during thereturn stroke of the motor piston II, the pin 4i is displaced againstthe action of compression spring 28, the pin 4I moving towards the rightin the drawing. With increased displacement of pin 4I toward the rightthe effective flow crosssection is reduced by reason of the tapering ofthe keyway or slot 42. This cushions the return stroke and meters thereturn iiow through keyway 42.

With the displacement of cylinder I during the power stroke, the sealingcollar 59 comes closer and closer to the mouth of the two channels 6Iand 49. Finally, it happens that, first, the mouth of channel 5I (and,possibly thereafter if displacement of motor piston I I is continued themouth of channel 69), is covered by the collar, so that the pump piston2 can no longer draw out pressure liquid during the suction part of thestroke from the annular spaces 58 and 6I), or from the reservoir 33. Inthis way, the pumping is terminated, and this also results intermination of the power stroke of the motor cylinder and motor piston.

With the lifting of check valve balls 24 and 27 from their seats bymaximum displacement of pump piston 2Q, (towards the left in thedrawing), the liquid contained in compression cylinder i can flow backduring the return stroke. The collar 59 which, incidentally is made ofmetal, is not stressed at any time by the closing of the passages EI and49, inasmuch as it is not under pressure.

.. There is connected to channel 6I, at the outer fluid through channel41,

wall of compression piston I I, a groove extending in the direction ofchannel 49. By means of this groove any hydraulic fluid in the annularspace 58, which remains after the termination of the stroke, is reducedto a minimum amount, and return of the pressure liquid into the annularspaces 60 and the supply receptacle 62 is facilitated.

It should of course be understood that various changes and modificationscan be made in my invention as herein described which would fall withinthe scope of my invention, and it is my intention that such changes ormodifications as are within the purview of the appended claims shall beconsidered as part of my invention.

What I claim is:

1. A hydraulic unit of the class described, comprising: a motorcylinder, a motor piston movably disposed within the motor cylinder andhaving a pump cylinderand closable pump inlet passage formed thereinsaid pump cylinder communicating through outlet check valve means withthe motor cylinder; a pump piston reciprocally disposed within the pumpcylinder; a reservoir adapted to contain hydraulic fluid; inlet checkvalve means carried by the motor piston and disposed to admit iluid fromthe reservoir through said pump inlet fluid passage into the pumpcylinder upon the suction stroke of the pump piston; and closure meanscarried by the motor cylinder and disposed to close said pump. inletfluid passage in response to a predetermined maximum movement of themotor piston relative to the motor cylinder, whereby the maximum strokeof the motor piston is limited by making the pump ineiective.

2. A hydraulic unit according to claim l, wherein said pump inlet fluidpassage comprises two open ends successively closable by said closuremeans.

3. A hydraulic unit according to claim 1, yfurther comprising a returnflow regulating member carried by the motor piston, sai-d regulatingmember being yieldingly movablewith respect to said motor piston andhaving a tapered passageway formed therein, said passageway beingprogressively restricted during the final period of motor retraction formetering the rate of said return flow.

4. A hydraulic unit of the class described, comprising: a pump piston; amotor piston having a pump cylinder formed therein, said pump pistonbeing reciprocably disposed within said pump cylinder, said motor pistonhaving rst and second fluid passages formed therein, said rst fluidpassage extending from the exterior portion of said motor piston intosaid pump cylinder; a rst check valve means carried by said motor pistonand disposed in said first iluid passage for admitting iiuid into saidpump cylinder; a reservoir adapted to receive hydraulic fluid; a motorcylinder within which said motor piston is movably disposed, a thirdiluid passage formed in -said motor piston, said third passage beingclosable and communicating between said reservoir and said rst uidpassage, said second fluid passage communicating between said pumpcylinder and said motor cylinder; a. second check valve meanscarried bysaid motor piston and disposed in said second iluid passage foradmitting uid from said pump cylinder into said motorl cylinder; andclosure means carried by said motor cylinder and effective after apredetermined of said motor piston and t0yk maximum movement close saidrst fluid passage.

5. A hydraulic unit according to claim 4, wherein said closure means isdisposed to close said third iiuid passage prior to the closure of saidfirst fluid passage.

6. A hydraulic unit according to claim 4, wherein said pump cylinder andsaid motor cylinder are coaxially disposed, said third fluid passagecommunicating with a space intermediate the internal surface of saidmotor cylinder and the external surface of said pump cylinder,

7. A hydraulic unit according to claim 4, fui'- ther comprising releasemeans carried by said pump cylinder and operative in an extreme pressurestroke position of travel of said pump piston for opening both saidfirst and second check Valve means to permit reverse fluid flowtherethrough; and flow retarding means disposed in said second uidpassage for metering the rate of said reverse flow during the finalperiod of motor retraction.

JAKOB LOEF.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATNTS Number Name Date 947,613 Gathrnann Jan. 25, 19101,080,062 Hess Dec. 2, 1913 1,201,180 Hennessy Oct. 10, 1916 1,611,703Zabriskie Dec. 21, 1926 1,709,000 Bolens Apr. 16, 1929 1,819,378 NilsonAug. 18, 1931 2,146,403 Nilson Feb. 7, 1939 2,187,279 Nilson Jan. 16,1940 2,359,060 Strom Sept. 26, 1944

